The Nakajima Mamoru
was an
air-cooled
14-cylinder double-row radial engine with a nominal power rating of
1800 horsepower (1342kW). The engine was considered economical on fuel
and had considerable potential for development, but it had some
teething problems. As a result, the Japanese Navy, in an
uncharacteristic effort to economize resources, demanded that Nakajima
cease production of the engine in favor of more proven designs such as
the Sakae and Homare. The Mamoru was
thus used only on early models of the B6N"Jill".